[Paleontology • 2006]
Yinlong downsi • A Basal Ceratopsian with Transitional Features from the Late Jurassic of northwestern China
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| Yinlong downsi
Xu, Forster, Clark & Mo, 2006
illustration: Andrey Atuchin || doi: 10.1098/rspb.2006.3566
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Although the Ceratopsia and Pachycephalosauria, two major ornithischian
groups, are united as the Marginocephalia, few synapomorphies have been
identified due to their highly specialized body-plans. Several studies
have linked the Heterodontosauridae with either the Ceratopsia or
Marginocephalia, but evidence for these relationships is weak, leading
most recent studies to consider the Heterodontosauridae as the basal
member of another major ornithischian radiation, the Ornithopoda. Here,
we report on a new basal ceratopsian dinosaur, Yinlong downsi gen. et. sp. nov.,
from the Late Jurassic upper part of the Shishugou Formation of
Xinjiang, China. This new ceratopsian displays a series of features
transitional between more derived ceratopsians and other ornithischians,
shares numerous derived similarities with both the heterodontosaurids
and pachycephalosaurians and provides strong evidence supporting a
monophyletic Marginocephalia and its close relationship to the
Heterodontosauridae. Character distributions along the marginocephalian
lineage reveal that, compared to the bipedal Pachycephalosauria, which
retained a primitive post-cranial body-plan, the dominantly quadrupedal
ceratopsians lost many marginocephalian features and evolved their own
characters early in their evolution.
Keywords: Ceratopsia; Marginocephalia; Ornithischia; Late Jurassic; Shishugou Formation
Systematic palaeontology
Ornithischia Seeley, 1887.
Heterodontosauriformes new taxon.
Marginocephalia, Sereno (1986).
Ceratopsia Marsh, 1890.
Yinlong downsi gen et sp nov.
Etymology: ‘Yin’ and ‘long’ mean ‘hiding’ and ‘dragon’ in Chinese, respectively, derived from the movie ‘Crouching Tiger, Hidden Dragon’ which was filmed in the locality where the holotype was found; the specific name is in memory of Mr Will Downs, who joined many palaeontological expeditions in China including the one with us in 2003, shortly before his death.
Holotype: IVPP V14530, a nearly complete skeleton missing only the distal tail (figure 1 and figures 1 and 2 of electronic supplementary material).
Holotype: IVPP V14530, a nearly complete skeleton missing only the distal tail (figure 1 and figures 1 and 2 of electronic supplementary material).
Locality and horizon: Wucaiwan, Junggar Basin, Xinjiang, China; upper part of Shishugou Formation, correlated with the Oxfordian stage of the early Late Jurassic (Chen 1996; Eberth et al. 2001).
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| Figure 2: IVPP V14530. (a) Skull and mandible in lateral view. (b) Skull in dorsal view.
Abbreviations: an, angular; d,
dentary; emf, external mandibular fenestra; en, external naris; f,
frontal; ff, fossa on frontals; fn, fossa on nasals; itf, infratemporal
fenestra; j, jugal; m, maxilla; p, parietal; pa, palpebral; pd,
predentary; pm, premaxilla; po, postorbital; q, quadrate; qj,
quadratojugal; r, rostral bone; sa, surangular; sq, squamosal; stf,
supratemporal fenestra; tr, tubercle row; ts, tubercle on surangular.
Scale bar, 2 cm.
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Xing Xu, Catherine A. Forster, James M. Clark and Jinyou Mo.
2006. A Basal Ceratopsian with Transitional Features from the Late
Jurassic of northwestern China. Proc. R. Soc. B. 273 (1598): 2135–2140. doi: 10.1098/rspb.2006.3566
Feng-Lu Han, Catherine A. Forster, James M. Clark & Xing Xu. 2015. Cranial anatomy of Yinlong downsi (Ornithischia: Ceratopsia) from the Upper Jurassic Shishugou Formation of Xinjiang, China. Journal of Vertebrate Paleontology. DOI: dx.doi.org/10.1080/02724634.2015.1029579
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